The present invention relates to a polishing pad used for a material to be polished such as semiconductors, electronic components, and the like. More specifically, it relates to a polishing pad for use in a polishing machine utilizing chemical-mechanical polishing (CMP) technology wherein a transparent window member is formed on a part of the polishing pad so as to let a laser beam or visible light pass therethrough to detect the end point of polishing rate (the amount of wafer material removed by polishing during a unit time interval) of the wafer surface during polishing.
In recent years, chip manufacturing has increasingly relied upon multi-layer structures to fabricate integrated circuits or ICs. During multi-layer IC circuit manufacturing, it is necessary that each layer of the IC circuit structure on a semiconductor wafer be planarized to maintain controlled electrical properties.
Planarization is performed by CMP (chemical mechanical planarization) also referred to as chemical-mechanical polishing using a polishing machine that comprises a lower platen having a circular rotating plate on which a polishing pad is attached; and an upper platen that presses a wafer onto the polishing pad; and a means for supplying a polishing slurry.
A polishing machine utilizing CMP technology employs a method for measuring the polishing rate while a wafer surface is being polished. The method requires that a laser beam be emitted from the rear side (platen side) of the polishing pad toward the wafer surface to be polished, which requires a transparent window member on a part of the polishing pad to allow the laser beam to pass therethrough.
To improve slurry dispersibility on the pad body surface, one can provide perforations, which are a group of minute openings, on the entire pad surface. This method has a drawback in that, if the openings are formed on a window member, slurry may leak through these openings or may agglomerate in the openings, which creates noise during measurement of the polishing rate of a wafer and adversely impacts accuracy of these measurements. Conventional technology has overcome this drawback by keeping the window member free from perforations. Nonetheless, the manufacturing methods required to produce these pads are inefficient.
In view of these concerns, there is a desire to manufacture a polishing pad in an effective manner that eliminates the cumbersome perforation steps of conventional technologies required to avoid puncturing the transparent window.
The invention provides a method of forming a transparent polishing pad. The first step forms a plurality of openings through a disk-shaped pad body. The plurality of openings is distributed about the disk-shaped pad body and a transparent window within a portion of the pad body and the transparent window. Then sealing the openings in the transparent window with a transparent material allows transport of polishing fluids through the openings in the disk-shaped pad body and prevents transport of the polishing fluids through the transparent window.